Insulator



Patented July 18, 1933 ALEXANDER P. BLOOD, OF NEW YORK; N. Y.

INSULATOR Application filed February 18, 1929. Serial No. 340,782.

element is in the form of a flattened coil encircling an insulation sheet and is held between two other insulation sheets. These sheets or plates have heretofore usually been cut from a sheet of mica of the desired thickness or from an artificial sheet made of mica splittings superposed to give the desired thickness and cemented together by means of shellac, silicate of soda or other cementing material. The pure mica sheets are comparatively expensive and in cutting them there is a very considerable waste in the form of trim. The artificial sheets made of splittings and cement are comp aratively stiff and although they may be made by use of the trim from pure mica sheets, the trim from the built up and cemented sheets cannot be again used. Thus a considerable amount of mica is wasted. a

The main object of my invention is to provide a mica insulator which is a great deal cheaper than either the pure mica or the sheet of cemented splittings, and which is equally effective as an insulator.

In carrying out my invention all of the trim from the sheets may be used in the making of other sheets, so that there is no waste of mica. Furthermore my improved sheets are made solely of mica splittings which are very inexpensive and do not require any shellac or other cement for holding the mica splittings together and in proper relative positions.

In carrying out my invention I use merely mica splittings and water or other readily i volatile liquid, and build. up the sheet to the desired thickness. The surface tension of the water will hold all of the mica splittings together and in the proper relative positions so long as the water remains between the mica layers. Thus the sheet with the pieces of mica of varying sizes hold together solely by the surface tension of the water, may be cut to the desired shape and assembled in the final position in respect to the heating element. In this final position it is subjected to pressure which drives out most of the water and i to gentle heat which drives out the rest so that only the mica splittings remain. Due to the fact that they are now under pressure they will hold their relative positions aiid 'serfve 5 just as effectively as an insulatorfas'woulfd a sheet of unsplit mica or a sheetin which: the mica splittings are cementedtogether:

By means of my invention Iverymaterially reduce the cost of the insulator, provide effective insulation, and use up all oithe mica because the trim from one sheet of." miea: splittings held together with Water, maylbe dried and the small pieces readily separated and used: in building up another sheet.

'My invention may be used as an'insulator in a Wide variety of different kind's crap: paratus, it only being essential that the condition of use be such that the insulatorisencased or held under sufiicient pressure to'prevent the shifting about of the'small pieces' of mica after the water has been dried. 0111;

' In the accompanying drawing Ihave illustrated merely one embodiment of my inventlon.

In the drawing:

Flg. 1 is a perspective view. of a heating element embodying my invention and adapted for use in a flat iron; M I

; Fig. 2 is a transverse section on the line 22 of Fig. 1, the partsbeing shown some what "diagrammatically and, greatly increased as to thickness; I i l l F 1g.3 is a plan View ofrthe device-shown in B 1g. l 'the outer metal casing being removed and a portion of the upper insulating sheet be ng broken away tofshow the heatingelement;

' Fig. 4 is a transverse section on the line 44 of Fig. 3, but very much enlarged as to thickness and spacing of the parts; and

- Fig. 5 is a plan view of the heating element' and the sheet upon which it iswound,

In carrying out my invention I employ mica splittings whichmay vary in thickness and in size, but all ofwhich are comparatively thin. These are thoroughly wet and distributed on a suitable support/so as-to build up a sheet of the size and thickness desired 19o so as to force'out a major portion of the water and to distribute the remaining water in very thin films between the contactmg surfaces of superposed splittings. These very thin films of water will exert such surface tension as will hold all of the pieces together and Wlll prevent any shifting. The sheet may then be handled the same as a sheet of pure mica or a cemented sheet, although, of course, somewhat greater care should be exercised to prevent undue pressure or bending strains.

-The sheet in this condition may be cut in a punch pressto' the desired shape, and if desired, it may be slotted or perforated in accordance with the use to which it is to be put.

A sheet 11 made up'of splittings merely heldtogether by films of water may be cut of a size and shape for use in a flat iron and has a central slot 12, rivet holes 13, and slots 14 for the leads to the heating element. Two such sheets may be employed, one beneath the 'heatingelement and the other above. The heating element itself may be wound upon a sheet made inthe same way as the sheet 11 above referred to.

As shown there are two comparatively narrow sheets 15 which are provided with notches along opposite sides and are placed upon opposite sides of the slot 12. An electric resistance element 16 is wound around two of these sheets 15 inseries and connected to leads 17 which may be extended through the slots 14 in one of the sheets 11. The successive turns of the resistance element are held in proper spaced relationship by winding the element in the notches on the edges of the sheets 15. The pieces of mica forming the sheets 15 will hold in place to permit the winding because the films of water between the sheets will dry'out only very slowly. p i

In making up the device the resistance element is placed between two of the sheets 11 and the entire device is subjected to pressure which will hold'alllo'f the parts permanently in positions -The device should be employed between two clamping plates, In Figs. 1 and 2 I have shown a facing plate 18 and a pressure plate 19, the two being permanently secured together by beading over a marginal flange on the plate 18 into engagement with the surface of the plate 19, andalso by means of rivets 20 extending through rivet holes in both plates and through the holes 13 in the insulating sheets 11. With the parts thus effectively and permanently clamped together sothat the small' pieces of mica cannot shift position, the entire device is subjected to gentle heat for such period as will effectively drive out all of the water forming the films between the superposed splittings. The

insulators will then be composed solely of mica splittings, and these will be as effectively held in place as though they had been cemented.

If the heating element is to be manufactured and sold-as a separate article of manufacture it should be permanently clamped in place between such plates as the plates 18 and 19. These plates serve not only to retain the mica sheets in assembled relationship but also serve to hold the splittings 1n distrlbuted relationship and to protect these sheets during use. g If the heating element is to be installed directly in the place of use at the time it is mamifactured, the plates 18 and 19 may be entirely omitted and the clamping action effected by two parts of the device itself, for instance the facing plate and pressure plate of the flat iron, Therefore by the term clamping plates I mean to include either two plates provided especially for the pur- L pose, or two plates which may form a part of the article in which the heating element is used and there perform the clamping function.

In carrying out my invention it will be noted that all. of the trim from the sheets 11 and 15 will be made up merely of mica splittings and water and that upon driving out this water such splittings may be used in making up additional insulating sheets.

Thus there is no waste of mica. There is likewise no cost for shellac or other cement, and the only material employed is the very inexpensive splittings. The water is merelv a' transitory element in that it holds the 3 splittings together during the time they are assembled to make up the sheet and during the cutting of the sheet and the placing of the latter in final position in respect to the electric conductor.

The device is as efficient as any mica insulation can be and is far cheaper to manufacture.

Although water is the preferred liquid for use in forming the thin films which temporarily hold the splittings together, it will,

of course, be obvious that any other volatile liquid may be employed, and it Wlll also be obvious that this may be a very weak solution of an adhesive which will have the same effect splittings to make the sheet of substantially uniform thickness, rigidly and permanently clampingsaid wetted splittings between opposed plates under pressure distributed throughout substantially the entire area of the opposite surfaces of the sheet toclamp said splittings together and prevent shifting thereof, and removing the liquid by evaporation whereby said splittings are permanently held in distributed relationship solely by said clamping plates.

2. An electrical insulator sheet, comprising a plurality of pieces of mica splittings of various sizes, each very much smaller than said sheet and distributed to make the sheet of substantially uniform thickness, plates eX- tending over substantially the entire area of opposite surfaces of said sheet, and means for permanently holding said plates together to clamp the mica splittings in distributed relationship and solely by pressure and prevent lateral shifting of the splittings during use.

3. The process of making an electrical insulation sheet, Which includes superposing mica splittings of varying sizes, each materially smaller than said sheet and Wetted with a volatile liquid, distributing said splittings to make the sheet of substantially uniform thickness, cutting the sheet to the desired size and shape, rigidly clamping the trimmed sheet of Wetted splittings under pressure between opposed plates and in such a manner as to permit the use of :said sheet in conjunction with said plates and to firmly hold said splittings together, to prevent shifting thereof, and to protect said sheet during use, and removing the liquid by evaporation While retaining the clamping plates, whereby said splittings are firmly held in distributed relationship solely by said clamping plates.

ALEXANDER P. BLOOD. 

